The invention relates to a method for igniting high-pressure discharge lamps. The invention relates primarily to an ignition method, which can be implemented in an electronic operating device and which addresses the problem of the willingness of discharge lamps to ignite in a polarity-dependent manner. Electronic ballasts have been used increasingly for a relatively long period of time. High-pressure discharge lamps are more difficult to handle in terms of their mode of operation than low-pressure discharge lamps, and the electronic operating devices are therefore more complex. Generally, high-pressure discharge lamps are operated with a low-frequency square-wave current, which is also referred to as “rocking DC operation”. This square-wave current fluctuates in the range between 100 Hz and 1 kHz, and ensures that the electrodes of the lamp are subjected to a uniform load, despite virtually DC operation. Until now, a full-bridge has usually been used for generating this signal. Since this results in high costs, in recent times there has been a switch to using a half-bridge for signal generation, and to incorporate the lamp in a balancing network including four coupling capacitors.
DE 10 2004 017 479 A1 has disclosed such a ballast. In this case, the lamp is operated using a low-frequency square-wave signal. For ignition purposes, such operating devices often have a superimposed ignition device which modulates a high ignition voltage pulse of several thousand volts onto the voltage present across the lamp. This modulation has previously been provided only in the positive-polarity quadrant or only in the negative-polarity quadrant of the lamp voltage. Thus, until now only positive or only negative ignition pulses have always been applied to the lamp. In this case, the voltage of the ignition pulses always remained the same in comparison with the no-load voltage applied to the lamp (the so-called takeover voltage). However, there are no lamps which develop unconventional properties when they are always subject to ignition pulses of the same polarity. They then act as a kind of diode, which brings about difficulties in the case of driving with a half-bridge and balancing capacitors. The capacitors are charged non-uniformly, which then has an effect on the voltage across the lamp, which can then no longer be brought into operation. The operating device attempts to ignite the lamp for a certain time. If this is unsuccessful, the operating device disconnects the voltage for a relatively long period of time before a new attempt is started. This time is necessary for the lamp to return to a state which does not immediately trigger a rectification effect again. This is extremely annoying for the user since it is necessary to wait for a long period of time before the luminaire actually emits light.
Various embodiments improve the method for igniting high-pressure discharge lamps in order to be able to start the lamps more quickly.